Chemistry Commons^™

Analysis Of Heme Iron Coordination In Dgcr8: The Heme-Binding Component Of The Microprocessor Complex, Hazel M. Girvan, Justin M. Bradley, Myles R. Cheesman, James R. Kincaid, Yilin Liu, Kazimierz Czarnecki, Karl Fisher, David Leys, Stephen E. J. Rigby, Andrew W. Munro

Chemistry Faculty Research and Publications

DGCR8 is the RNA-binding partner of the nuclease Drosha. Their complex (the “Microprocessor”) is essential for processing of long, primary microRNAs (pri-miRNAs) in the nucleus. Binding of heme to DGCR8 is essential for pri-miRNA processing. On the basis of the split Soret ultraviolet–visible (UV–vis) spectrum of ferric DGCR8, bis-thiolate sulfur (cysteinate, Cys^–) heme iron coordination of DGCR8 heme iron was proposed. We have characterized DGCR8 heme ligation using the Δ276 DGCR8 variant and combined electron paramagnetic resonance (EPR), magnetic circular dichroism (MCD), electron nuclear double resonance, resonance Raman, and electronic absorption spectroscopy. These studies indicate DGCR8 bis-Cys heme …

Water-Assisted Oxygen Activation During Selective Oxidation Reactions, Hung-Vu Tran, Hieu A. Doan, Bert D. Chandler, Lars C. Grabow

Chemistry Faculty Research

The selective functionalization of hydrocarbons with oxygen to produce valuable commodity chemicals is inherently challenging, because of the thermodynamic stability of the complete combustion products. Emerging green synthesis routes and sustainable energy production also rely on the success of selective oxidation reactions. As one of the unselective by-products, water is always present under reaction conditions and numerous studies indicate that the catalytic activity and selectivity of selective oxidation reactions may be tuned by judiciously controlling the water content during the reaction. Some experimentally verified examples include the preferential oxidation of carbon monoxide, direct hydrogen peroxide synthesis, propene epoxidation and alcohol …

The San1 Ubiquitin Ligase Functions Preferentially With Ubiquitin-Conjugating Enzyme Ubc1 During Protein Quality Control, Rebeca Lea Ibarra

UNLV Theses, Dissertations, Professional Papers, and Capstones

Protein quality control (PQC) is a critical process wherein misfolded or damaged proteins are cleared from the cell to maintain protein homeostasis. In eukaryotic cells, the removal of misfolded proteins is primarily accomplished by the ubiquitin-proteasome system (UPS). In the UPS, ubiquitin-conjugating enzymes and ubiquitin ligases append poly-ubiquitin chains onto misfolded protein substrates signaling for their degradation. The kinetics of protein ubiquitylation are paramount since a balance must be achieved between the rapid removal of misfolded proteins versus providing sufficient time for protein chaperones to attempt refolding. To uncover the molecular basis for how PQC substrate ubiquitylation rates are controlled, …

Structural Behavior Of Nbsexte2-X Superconductors Under High Pressure, Vahe Mkrtchyan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Niobium chalcogenide compounds have recently gained a great deal of interest due to the fact that a superconducting phase coexists with the charge density wave state (CDW), as well as their potential for numerous applications. Two superconducting compositions, NbSexTe2-x (x=2, 1.5) were prepared by solid state route using high purity Nb, Se, and Te powders. Powder X-ray diffraction patterns collected at ambient conditions for NbSe2 and NbSe1.5Te0.5 showed a single phase with hexagonal crystal structure, with space group P63mmc. High-pressure X-ray diffraction measurements were performed at the Advanced Photon Source at Argonne National Laboratory to investigate structural stability up to …

The Proof Is In The Pots: Residue Analysis Of Virgin Branch Puebloan Ceramics, Brenna Lynn Wilkerson

UNLV Theses, Dissertations, Professional Papers, and Capstones

This study focuses on better understanding diet and subsistence strategies among Virgin Branch Puebloan groups living in the Moapa Valley in southern Nevada and on the Shivwits Plateau in northwestern Arizona. Gas chromatography-mass spectrometry (GC-MS) was used to identify absorbed food residues in three types of Virgin Branch Puebloan ceramics (Moapa Gray Ware, Shivwits Ware, and Tusayan Virgin Series). The data produced by the residue analysis were used to compare patterns of subsistence between Virgin Branch Puebloan sites in the lowlands along the Muddy River and at upland sites on the Shivwits Plateau as these two areas have different environments …

Efficient Method For Calculations Of Ro-Vibrational States In Triatomic Molecules Near Dissociation Threshold: Application To Ozone, Alexander Teplukhin, Dmitri Babikov

Chemistry Faculty Research and Publications

A method for calculations of rotational-vibrational states of triatomic molecules up to dissociation threshold (and scattering resonances above it) is devised, that combines hyper-spherical coordinates, sequential diagonalization-truncation procedure, optimized grid DVR, and complex absorbing potential. Efficiency and accuracy of the method and new code are tested by computing the spectrum of ozone up to dissociation threshold, using two different potential energy surfaces. In both cases good agreement with results of previous studies is obtained for the lower energy states localized in the deep (∼10 000 cm−1) covalent well. Upper part of the bound state spectrum, within 600 cm−1 below dissociation …

Petrographic And Geochemical Characteristics Of The Kiejo, Rungwe And Ngozi Volcanic Rocks, Southern Tanzania: Implication For Tectonic Activities And Magmatic Differentiation, Athanas S. Macheyeki

Tanzania Journal of Science

Rock samples were collected from the Kiejo, Rungwe and Ngozi volcanoes, southern Tanzania. Results show that, in the Ngozi and Rungwe volcanoes, magma cooled relatively fast. After large part of the magma had crystallized, nucleation of crystals at a relatively slow rate crystallized from interstitial fluids of the primary magma that had already crystallized fine grained minerals resulting into large grains of minerals. In the Kiejo volcano, both zoned and unzonned olivine crystals exist; unzoned crystals being primary and the zoned ones are secondary. Such observations also indicate that the magma responsible for these rocks had interstitial fluids that crystallized …

Intramolecular 1,5-C(Sp3)–H Radical Amination Via Co(Ii)-Based Metalloradical Catalysis For Five-Membered Cyclic Sulfamides, Hongjian Lu, Kai Lang, Huiling Jiang, Lukasz Wojtas, X Peter Zhang

Chemistry Faculty Publications

Co(II)-based metalloradical catalysis (MRC) proves effective for intramolecular 1,5-C–H amination of sulfamoyl azides under neutral and nonoxidative conditions, providing a straightforward approach to access strained 5-membered cyclic sulfamides with nitrogen gas as the only byproduct. The metalloradical amination system is applicable to different types of C(sp³)–H bonds and has a high degree of functional group tolerance. Additional features of the Co(II)-catalyzed 1,5-C–H amination include excellent chemoselectivity toward allylic and propargylic C–H bonds. The unique reactivity and selectivity profile of the Co(II)-catalyzed 1,5-C–H amination is attributed to the underlying radical mechanism of MRC.

Multiple New-Particle Growth Pathways Observed At The Us Doe Southern Great Plains Field Site, Anna L. Hodshire, Michael J. Lawler, Jun Zhao, John Ortega, Coty Jen, Taina Yli-Juuti, Jared F. Brewer, Jack K. Kodros, Kelley C. Barsanti, Dave R. Hanson, Peter H. Mcmurry, James N. Smith, Jeffery R. Pierce

Civil and Environmental Engineering Faculty Publications and Presentations

New-particle formation (NPF) is a significant source of aerosol particles into the atmosphere. However, these particles are initially too small to have climatic importance and must grow, primarily through net uptake of low volatility species, from diameters ∼ 1 to 30–100 nm in order to potentially impact climate. There are currently uncertainties in the physical and chemical processes associated with the growth of these freshly formed particles that lead to uncertainties in aerosol-climate modeling. Four main pathways for new-particle growth have been identified: condensation of sulfuric-acid vapor (and associated bases when available), condensation of organic vapors, uptake of organic acids …

Minimizing Corrosion Of Outdoor Metalworks Using Dispersed Chemically Stabilized Nanoclays In Polyvinylidene Fluoride Latex Coatings, Natasja Alexandria Swartz, Capri A. Price, Tami Lasseter Clare

Chemistry Faculty Publications and Presentations

Nanoclays are small enough to appear optically transparent, yet they have large surface-to-volume and high aspect ratios that can significantly inhibit water diffusion when incorporated into protective coatings. Clear coatings, which minimally affect the aesthetics of metalworks, are commonly applied to outdoor metalworks, such as sculptures, to prevent and slow corrosion. In recent years, waterborne clear coatings, rather than solvent-based clear coatings, are increasingly used in many applications to reduce the quantity of volatile organic components in the formulation, yet the performance of dry films produced from waterborne colloidal suspensions is generally poorer. In this work, we aim to improve …

Binding Properties Of Large Antiviral Polyamides (Pa1 And Pa25) And Natural Product Derivatives As Inhibitors Of Serine Hydrolases, Elena Vasilieva

Dissertations

Polyamides are a class of DNA minor groove binders that were developed from the natural product Distamycin A. PA25 (20-ring PA) showed better activity (3-fold) in the elimination of HPV16 episomes than PA1 (14-ring PA). Binding studies of PA1 and PA25 were performed in the long control region of HPV16 (7348-122 bp). PA1 showed similar binding affinity to perfect match and single mismatch binding sites. PA1 bound to double, triple, and quadruple mismatch sites with lower affinity. PA25 bound with similar binding affinity to perfect through triple mismatch binding sites. PA25 bound quadruple mismatch sites and nonspecifically. Therefore, it was …

Fulleretic Well-Defined Scaffolds: Donor–Fullerene Alignment Through Metal Coordination And Its Effect On Photophysics, Derek E. Williams, Ekaterina A. Dolgopolova, Danielle C. Godfrey, Evgeniya D. Ermolaeva, Perry J. Pellechia Dr., Andrew B. Greytak Prof. Dr., Mark Smith Dr., Stanislav M. Avdoshenko, Dr., Alexey A. Popov Dr., Natalia B. Shustova Prof. Dr.

Faculty Publications

Herein, we report the first example of a crystalline metal–donor–fullerene framework, in which control of the donor–fullerene mutual orientation was achieved through chemical bond formation, in particular, by metal coordination. The 13C cross-polarization magic-angle spinning NMR spectroscopy, X-ray diffraction, and time-resolved fluorescence spectroscopy were performed for comprehensive structural analysis and energy-transfer (ET) studies of the fulleretic donor–acceptor scaffold. Furthermore, in combination with photoluminescence measurements, the theoretical calculations of the spectral overlap function, Förster radius, excitation energies, and band structure were employed to elucidate the photophysical and ET processes in the prepared fulleretic material. We envision that the well-defined fulleretic donor–acceptor …

Mida Boronates Are Hydrolysed Fast And Slow By Two Different Mechanisms, Jorge A. Gonzalez, O. Maduka Ogba, Gregory F. Morehouse, Nicholas Rosson, Kendall N. Houk, Andrew G. Leach, Paul H.-Y. Cheong, Martin D. Burke, Guy C. Lloyd-Jones

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

MIDA boronates (N-methylimidodiacetic boronic acid esters) serve as an increasingly general platform for building-block-based small molecule construction, largely due to the dramatic and general rate differences with which they are hydrolysed under various basic conditions. Yet the mechanistic underpinnings of these rate differences have remained unclear, hindering efforts to address current limitations of this chemistry. Here we show that there are two distinct mechanisms for this hydrolysis: one is base-mediated and the other neutral. The former can proceed more than three orders of magnitude faster, and involves rate-limiting attack at a MIDA carbonyl carbon by hydroxide. The alternative ‘neutral’ hydrolysis …

C60 And Sc3N@C80(Tmb-Ppo) Derivatives As Constituents Of Singlet Oxygen Generating, Thiol-Ene Polymer Nanocomposites, Emily M. Barker, Ashli R. Toles, Kyle A. Guess, J. Paige Buchanan

Faculty Publications

Numerous functionalization methods have been employed to increase the solubility, and therefore, the processability of fullerenes in composite structures, and of these radical addition reactions continue to be an important methodology. C₆₀ and Sc₃N@C₈₀ derivatives were prepared via radical addition of the photodecomposition products from the commercial photoinitiator TMB-PPO, yielding C₆₀(TMB-PPO)₅ and Sc₃N@C₈₀(TMB-PPO)₃ as preferred soluble derivatives obtained in high yields. Characterization of the mixture of isomers using standard techniques suggests an overall 1PPO:6TMB ratio of addends, reflecting the increased reactivity of the carbon radical. Although, a higher …

Expanding The Versatility Of Nano Assembled Capsules As Platform Of Potential High Payload Mri Contrast Agents, Annah Farashishiko

Dissertations and Theses

Magnetic resonance imaging (MRI) has become a powerful clinical modality in diagnostic medicine. It is non-invasive and offers high spatial and temporal resolution. The goal of molecular imaging is to reveal the pathophysiology underlying the observed anatomy and diagnose diseases. The detection of pathological biomarkers can lead to early recognition of diseases and improved monitoring for recurrence. Clinically available contrast agents are limited in their discrimination of contrast between tissues and they tend to have very high detection limits. Because biomarkers are very low in concentration there is a need for high payload deposition of contrast agent (CA) and targeted …

Effects Of Angular Deformation On The Energetics Of The Sn2 Reaction, Vincent De Paul Nzuwah-Nziko, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

Quantum calculations are applied to a number of model SN2 reactions. The halides F-, Cl-, and Br- were allowed to attack the central C atom of a set of CH2RI molecules, with R= H, CH3, CH=CH2, C≡CH, and C≡N. For each system the X∙∙C∙∙I angle was distorted in set increments from the optimized value, and the activation energy computed for each angle. The energy of the transition state rose in conjunction with this deformation. However, the distortion energy of the initial X-∙∙CH2RI reaction complex was similar in magnitude. As a result, the activation energy of the reaction was quite insensitive …

Interpretation Of Spectroscopic Markers Of Hydrogen Bonds, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

Quantum calculations are used to examine whether a AH∙∙D H-bond is unambiguously verified by a downfield shift of the bridging proton’s NMR signal or a red (or blue) shift of the AH stretching frequency in the IR spectrum. It is found that such IR band shifts will occur even if the two groups experience weak or no attractive force, or if they are drawn in so close together that their interaction is heavily repulsive. The mere presence of a proton-acceptor molecule can affect the chemical shielding of a position occupied by a proton-donor by virtue of its electron density, even …

58th Annual Rocky Mountain Conference On Magnetic Resonance

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 58th annual meeting of the Rocky Mountain Conference on Magnetic Resonance, co-endorsed by the Colorado Section of the American Chemical Society and the Society for Applied Spectroscopy. Held in Breckenridge, Colorado, July 17-21, 2016.

Discovery And Characterization Of The Proteins Involved In The Synthesis Of N⁶-Threonylcarbamoyl Adenosine, A Nucleoside Modification Of Trna, Christopher Wayne Deutsch

Dissertations and Theses

N6-threonylcarbamoyl adenosine (t⁶A) is a universally conserved tRNA modification found at position 37 of tRNAs which decode ANN codons. Structural studies have implicated its presence as a requirement for the disruption of a U-turn motif in certain tRNAs, leading to the formation of properly structured anticodon stem loop. This structure is proposed to enhance the base pairing between U₃₆ of tRNA and A₁ of the codon which aids in translational frame maintenance.

Despite significant effort since its discovery in the 1970s the enzymes involved in its biosynthesis remained undiscovered. Bioinformatic analysis identified two proteins as likely …

Synthesis And Structure Activity Relationship Of Novel Small Molecules As Inhibitors Of Plasminogen Activator Inhibitor-1, Karl Michael Upman

Master's Theses and Doctoral Dissertations

Plasminogen activator inhibitor type-1 (PAI-1) is a member of the serine protease inhibitor (serpin) family. PAI-1 is involved in the regulation of fibrinolysis, which is the breakdown of blood clots. PAI-1 inhibits serine proteases tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA), which are key factors in fibrinolysis. Excess levels of PAI-1 have also been shown to increase the risk of diabetes, stroke, and atherosclerosis, as well as tumor development. Previous attempts at synthesizing a practical drug for the regulation of PAI-1 have not been successful; therefore, it has been the purpose of this study to further advance progress …

Diastereoselective Aza-Cope Rearrangement-Mannich Cyclizations Of Conformationally Mobile Iminium Cations, Joshua Hunt

Master's Theses and Doctoral Dissertations

We have developed a Lewis-acid catalyzed, diastereoselective aza-Cope rearrangement— Mannich cyclization (ACM) to form acyl pyrrolidines from conformationally mobile substrates. Earlier studies from our lab have shown that substituted acyl pyrrolidines can be synthesized with diastereoselectivity of 50:1 trans to cis, and that unsubstituted pyrrolidines can be synthesized with 13:1 enantioselectivity. This study attempted to observe the stereochemical outcomes of the ACM for disubstituted pyrrolidine systems using oxazolidine starting materials. A proof of concept dimethyl-substituted oxazolidine was subjected to ACM conditions, producing the pyrrolidine with good yields. However, when methyl-phenyl substituted oxazolidine was subjected to ACM conditions, undesired byproduct …

Synthesis Of A Small Molecule Nitrosocysteine Inhibitor To Reduce The Activity Of Caspase-1, Catherine A. Shamblen, Caitlin E. Karver

DePaul Discoveries

Caspase-1 is an enzyme that is overactive in autoimmune and autoinflammatory diseases cleaving pro-interleukin-1β to the cytokine interleukin-1β (IL-1β), which leads to inflammatory symptoms. The inhibition of caspase-1 will cause a decrease in the concentration of interleukin-1β (IL-1β), resulting in the reduction of inflammatory symptoms. Recent research has revealed that the appending of a nitric oxide (NO) or nitroxyl (HNO) donating group to non-steroidal anti-inflammatory drugs (NSAIDs) reduced, or avoided, the side effects caused by currently available treatments. A small molecule based on a known caspase-1 inhibitor with a nitrosocysteine appended on was synthesized to look at the effect of …

Serendipitous Discovery Of A New Method For The Catalytic Synthesis Of Indole-Fused Benzazepanes, Edward Gluzman, Paul A. Vadola

DePaul Discoveries

We report here on our investigations into the application of 1,5-hydride transfer cyclization mechanisms to the synthesis of 2,3-disubstituted benzofurans and indoles. We found that PtI₄ in MeCN at 120 ºC was indeed capable of activating the alkyne, however, the expected 2,3-disubstituted indole product was not observed. Instead we isolated an indolyl-3-benzazepane via an unexpected intramolecular Steven’s rearrangement/ring expansion. While this transformation has been previously reported our method may prove to have increased substrate scope and more practical reaction conditions. Further studies are underway to optimize the reaction conditions and to fully explore the scope and mechanism of the …

Electrochemistry And Spectroscopy Of A Molybdenum Porphyrin Compound, Jay S. Bhanot, Kyle A. Grice

DePaul Discoveries

Carbon dioxide has been a problematic greenhouse gas since the beginning of the industrial age. In an effort to remediate its effects on the climate, multiple techniques have been utilized in the chemical and electrochemical reduction of CO₂. Homogeneous electrocatalysis for carbon dioxide reduction has been a topic of increasing interest. However, a full examination of the catalytic performance of early transition metals supported by macroligands has yet to be done. The research reported involves synthesis of a chelate of molybdenum within a tetraphenylporphyrin, and then synthesis, purification, and characterization of its ability to reduce carbon dioxide. The …

Synthesis And Studies Of Cyclopentadienyl Molybdenum Complexes, Cesar Saucedo, Kyle A. Grice

DePaul Discoveries

The synthesis and electrochemical responses of [CpMo(CO)₃]₂, CpMo(CO)₃I, CpMo(CO)₃(OTf), and [CpMo(bpy)(CO)₂] (Cp = cyclopentadienyl, bpy = 2,2’-bipyridine, OTf = trifluoromethansulfonate) in organic solvent are reported. Transition metal compounds such as Re(bpy)(CO)₃Cl have been shown to be effective carbon dioxide reduction catalysts. The molybdenum metal complexes studied herein were examined under argon and carbon dioxide gas for the potential reduction of carbon dioxide. Proton Nuclear Magnetic Resonance (NMR) spectroscopy, infrared (IR) spectroscopy and an electrochemical method know as cyclic voltammetry were used to gather data on the complexes. Electrochemical …

Interactions Between Temozolomide And Quercetin, Okuma Emile Kasende, Vincent De Paul Nzuwah-Nziko, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

Temozolomide and quercetin are both molecules with important pharmaceutical activity, whose effects can mutually enhance one another when clinically applied simultaneously. Quantum chemical calculations are used to examine how the two molecules might interact with one another. The most stabilizing force arises when the aromatic systems of the two molecules are arranged parallel to one another. These stacked configurations are reinforced by H-bonds, but geometries containing only H-bonds, without the aromatic stacking, are much less stable, even if the H-bonds are short and strong. Comparison between B3LYP and B3LYP-D binding energies allows an evaluation of dispersion energy, which is found …

Co7se8 Nanostructures As Catalysts For Oxygen Reduction Reaction With High Methanol Tolerance, Jahangir Masud, Manashi Nath

Chemistry Faculty Research & Creative Works

Co₇Se₈ nanostructures electrodeposited on glassy carbon (GC) electrodes show high efficiency for oxygen reduction reaction (ORR) with high methanol tolerance as compared to Pt electrocatalysts. In the presence of methanol, the onset potential for the ORR at Pt/GC is shifted from 0.931 V (vs reversible hydrogen electrode (RHE)) to 0.801 V (vs RHE), whereas it remains the same (0.811 V vs RHE) at Co₇Se₈/GC in the presence and absence of methanol in 0.5 M H₂SO₄ solution. The Co₇Se₈/GC electrodes also showed high cyclability in the presence …

Multifunctional Heterocyclic Scaffolds For Hybrid Lewis Acid/Lewis Base Catalysis Of Carbon–Carbon Bond Formation, Dennis Wiedenhoeft, Adam R. Benoit, Yibiao Wu, Jacob D. Porter, Elisia Meyle, Teresa H.W. Yeung, Raechel Huff, Sergey V. Lindeman, Chris Dockendorff

Chemistry Faculty Research and Publications

No abstract provided.

Layered Xerogel Films Incorporating Monolayer Protected Cluster Networks On Platinum Black Modified Electrodes For Enhanced Sensitivity In 1st Generation Uric Acid Biosensing, Mulugeta B. Wayu, Michael J. Pannell, Michael C. Leopold

Chemistry Faculty Publications

Amperometric uric acid (UA) biosensing schemes incorporating networks of alkanethiolate‐protected gold nanoparticles, monolayer protected clusters (MPCs), and platinum black (Pt‐B) electrode modification through the layer‐by‐layer construction of xerogels are investigated. MPC doping and Pt‐B augmentation are implemented within hydroxymethyltriethoxysilane xerogel bilayers at platinum electrodes. The first xerogel adlayer is doped with an MPC network and houses uricase for the enzymatic reaction required for first‐generation schemes. Polyluminol–aniline and polyurethane are used as selective/stabilizing interfacial layers. The sensing performance with and without Pt‐B and/or MPC doping is assessed by amperometry with standardized UA injections. The use of each individual material results in …

Synthesis, Characterization, And Pre-Ceramic Properties Of Π-Conjugated Polymers Based On Ni(Ii) Complexes Of Goedken’S Macrocycle, Joseph A. Paquette, Joe Gilroy

Chemistry Publications

Nickel(II) complexes of Goedken’s macrocycle bearing alkyne substituents were copolymerized with 2,7-dibromo-9,9-dihexylfluorene, 2,5-dibromo-3-hexylthiophene, and 1,4-dibromo-2,5-bis(hexyloxy)benzene via microwave-induced Sonogashira cross-coupling reactions to produce copolymers 6F, 6T, and 6B. The spectroscopic and electrochemical properties of the copolymers were examined and compared to model compounds. Specifically, each polymer exhibited a nickel-based absorption centered at ca. 589 nm and two π → π* transitions between 272 and 387 nm. While the copolymers did not exhibit extended π conjugation, the nature of the organic spacer did affect the high energy transitions. Furthermore, each copolymer underwent two ligand-based one-electron oxidations at potentials …